Error in reading and writing CSV format file in python

[inshu chauhan]

On Mon, Feb 11, 2013 at 1:26 PM, Steven D'Aprano <
steve+comp.lang.python at pearwood.info> wrote:

> inshu chauhan wrote:
>
> > In the programme below I am trying to read two csv format files and
> > process them and write a new file with some of theirs data.
> >
> > import csv
> > f1_reader = csv.reader(open(r"Z:\Weka
> > work\Feature_Vectors_Fullset_00.arff"))
> > f2_reader = csv.reader(open(r"Z:\Weka
> > work\Feature_Vectors_Fullset_00_noxy+class.arff"))
> > nf = open(r"Z:\Weka work\classified_image00_withoutxy.arff", "w")
> >
> > while True:
> >     l1 = f1_reader.next()
> >     while len(l1) != 12:
> >         l1 = f1_reader.next()
> >     l2 = f2_reader.next()
> >     while len(l2) != 11:
> >         l2 = f2_reader.next()
> >
> >     ix = l1[0].strip()
> >     iy = l1[1].strip()
> >     classification = l2[8].strip()
> >
> >     print >> nf, ix, iy, classification
> >
> > nf.close()
> >
> > This programme is giving me this error now :
> >
> > Traceback (most recent call last):
> >   File "Z:\Weka work\final_image_classificationwithoutxy.py", line 16, in
> > <module>
> >     l2 = f2_reader.next()
> > StopIteration
> >
> >
> > what could be a possible reason to StopIteration ???
>
> next() raises StopIteration when there is nothing else to return.
>
>
> py> it = iter([1, 2, 3])
> py> it.next()
> 1
> py> it.next()
> 2
> py> it.next()
> 3
> py> it.next()
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> StopIteration
>
>
> You have reached the end of the file and there is nothing else for the CSV
> reader to return, so it raises StopIteration.
>


But why does it has nothing to return so early before traversing the whole
file ? Is there any way it can be corrected ?  And also the programme isn't
writing anything to the file ?

>
>
>
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